In the past, patients needing assistance to reach standing positions had to depend upon human or prior art mechanical support. If supported solely by nursing or therapy personnel, there is a higher risk of injury for both the patient and the assisting personnel. Patients could lose support lifting themselves or being lifted and sustain a fall. Nursing or therapy personnel could sustain back or other muscle injuries while preventing the patient fall or while in the act of lifting and moving the patient, especially when a patient is an obese or morbidly obese person (morbidly obese being at least two times the recommended weight for a given height).
Prior art mechanical devices may also at times require a level of assistance from the patient themselves to accomplish the standing task. Prior art mechanical devices also do not address the true nature of motion required to move from a sitting to a standing position. In fact, it is complex. To mirror the same movement required to achieve an independent sit to stand, the shoulders must lean forward out over the knees placing the center of mass over the feet. The feet are then prepared to support the body weight in line as the torso is raised to an erect posture.
Prior art devices either lifted by the upper torso only, which can possibly overload the delicate upper body structure (most commonly the axillary [armpit] area and specifically the shoulder joints and tendons), or by the upper torso and hips, which when employed at the same angle and speed during the lift tends to keep the patients in a crouching or semi-crouching position.
Devices that facilitate a patient moving from sitting and standing positions typically utilize one actuator that raises a lift element (e.g., a boom). One end of the boom is fixed at an axis point and when raised describes an arc that exists in the vertical plane. The actuators are either electrical or mechanical. The manual type typically employs a lever or piston arrangement. Such devices operate in a manner that is similar to the way in which a hoist lifts an engine out of an automobile engine bay. While raising the boom in a vertical arc, the shoulders and trunk are pulled and lifted upward bringing the person from a sitting to a semi-crouching position. As the boom completes its arc the pulling motion shifts from primarily vertical to primarily forward to raise the patient from a crouching position to an erect posture.
Most of the prior art devices are sufficiently stable to allow a smaller or average size person to be lifted from a sit to a stand position with the assistance of nursing or therapy personnel. However, instabilities inherent in lifting patients who are large or obese and those who are unable to maintain their own balance, may cause lateral forces to be exerted on the boom as it moves through its vertical arc. Such lateral forces may tend to cause a shifting of the patient's center of mass, which in turn may cause the undesirable side loading of the actuators. Such side loading may contribute to the instability of the device and may compromise the structural integrity of the actuators.
What is needed is an apparatus that allows a patient of any size, including obese and morbidly obese, to securely and safely move between sitting and standing positions with a minimum of risk of injury to themselves or to those who are assisting them; and that can operate with minimal risk of equipment failure while supporting any patient.